Thinking out loud about weather

I grew up in central Virginia about two hours south of DC. My high school years were some of the best of my life as I had a great group of friends. One of the things we planned from an early age was The Great Snowball Fight. Inspired by the success of The Great Watergun Fight which involved careful planning, splitting the group into teams, establishing rules for appropriate ammunition, automatic water guns, crates of water balloons, etc. So spectacular was TGWF, which took place during the summer before 10th grade, we made our grand plans for TGSF. It was going to be epic.

Central Virginia was usually good for one good snowstorm of 6 inches or so per winter. We waited that winter, but the snow never came. We waited the next winter, but the snow never came. We waited yet another winter, but the snow never came. We graduated, went off the college, and went on with the rest of our lives. The Great Snowball Fight never took place.

Those were 3 straight years without a significant snowstorm. Yet this year, like DC, central Virginia has been hit hard with snow, the fourth storm being forecast for next week. Though the memory of my childhood is hazy, there were a couple of winters where we had multiple heavy snowstorms like this year, though not as severe. These anecdotes point to a conjecture: snowfall is chaotic. I'm not a mathematician but this pattern is "chaotic" as I grok the term.

One explanation for this chaotic pattern might be at the "meta" level. It's not so much the nature of snowstorms that we should look at, but the set of higher-level conditions that give rise to snowstorms. For example, during the winters with repeat snowstorms, I seem to recall the weatherman saying that the jet stream had dipped down to right over the mid-Atlantic states. This brings south the cold air from north of the jet stream allowing it to mix with warm moist air from the Atlantic resulting in precipitation, which if it's cold enough, will result in snow. As long as the jet stream stayed that far south, conditions were ripe for snow rather than rain. The meta-condition (the position of the jet stream) would explain the chaotic nature of snowstorms. In the rare event that the jet stream was located more South than usual, central Virginia was hit with multiple heavy snowstorms. If the jet stream was in its usual position, snowstorms were rare.

One implication comes from the fact that I don't think people understand chaotic systems well. This is why any seemingly abnormal weather brings out a search for a greater meaning which doesn't exist when taken in context of a long term view.

Share this